RFR(trivial): 8232768: Configuration with --disable-cds --enable-generate-classlist should be reported as an error

[Jie Fu]

Hi all,

May I get reviews for this one-line change?

JBS:    https://bugs.openjdk.java.net/browse/JDK-8232768
Webrev: http://cr.openjdk.java.net/~jiefu/8232768/webrev.00/

This kind of configuration, with both --disable-cds and 
--enable-generate-classlist, will fail.
The failure is caused by -XX:DumpLoadedClassList [1], which doesn't work 
as expected when cds is disabled.

It might be better to produce an error.

Thanks a lot.
Best regards,
Jie

[1] 
http://hg.openjdk.java.net/jdk/jdk/file/ca620b06b5c9/make/GenerateLinkOptData.gmk#l68